Every person I've known to have their FB account deleted also happened to be people who posted inflammatory, toxic content on a daily basis. most of them also acted that way in PMs with people, but on an even more terrible level. Harassment level conversations, and probably a much larger scope than I was directly aware of.
I am not at all convinced that Facebook just deletes accounts for no reason. Sure, high-profile people get maliciously flagged sometimes, but I seriously doubt these randoms who get deleted are telling the entire story.